Can We Determine Whether Training with Food Is Positive or Negative Reinforcement?

A blue box clicker and pile of dry kibble

If your dog is really hungry, what learning process will be involved here?

Yes we can. This question was pretty well answered in the 1950s.

Note: You need a basic understanding of the processes (often called quadrants) of operant learning for the discussion in this post to be meaningful. You can read my post, Operant Learning  Illustrated by Examples, to get the basics.

Lately I’ve been reading a lot of remarks that seek to minimize the difference between positive and negative reinforcement. Some people claim that you can’t determine which process is at work in any reinforcement scenario  (continuum fallacy, anyone?), and it’s even been argued that the terms “positive” and “negative” should be abolished. More on that in a later post, but if you pick up any new edition of a learning theory textbook, guess what? That point of view may be mentioned but the terms are still in use.

I got curious about the food argument so I gathered up some articles I had and did a little poking around in the psych journals.

To review:

  • Positive reinforcement: Something is added after a behavior, which results in the behavior happening more often.
  • Negative  reinforcement: Something is removed after a behavior, which results in the behavior happening more often.

Both processes increase behaviors, but most trainers feel there is a big difference between the two methods. Negative reinforcement involves an aversive (the thing that gets removed), and most trainers in the positive reinforcement oriented community want to avoid that. But there seems to be a growing minority that either truly doesn’t perceive a difference or is focused on some gray areas and generalizing from those.

Indeterminate Situations

There are indeed some situations where it is very difficult or impossible to determine the major process. The classic example is that of thermostat adjustment. If you are a little bit cold and go turn your thermostat up 2 degrees and the furnace comes on, are you adding heat or reducing cold? Most people would say the latter (negative reinforcement), but that heat can sure feel pleasurable and luxurious in its own right when it comes on. The situations that don’t fit well into one process or another generally have in common that they deal with a continuum of states and not discrete things that are added or removed.

So yeah, there are some scenarios where the primary process can’t easily be determined.

But food intake is not one of them.

Here’s how the argument is usually presented:

People who train with food are employing a negative reinforcement protocol because food removes the aversive state of hunger.

I have seen this claimed by force trainers but also a few people in the positive reinforcement (oops! maybe they wouldn’t call it that) community. It is often played like some sort of trump card, but it is as out of date as dominance theory.

What I haven’t seen is anybody pointing out is that there were multiple experiments performed in the 1950s that successfully separated out the positive reinforcement qualities of food that were independent of assuaging hunger. So here we go.

The Studies

In 1950 Sheffield and Roby published, “Reward value of a non-nutritive sweet taste.” The abstract from APA PsychNet:

After showing that hungry rats will ingest significantly more of a 1.3 gram/liter saccharine solution than satiated control animals, the hungry rats were trained on a single unit T-maze with a saccharine solution reward. Learning was rapid and showed a high positive relation between correct choice and speed on the one hand and rate of ingestion of the saccharine reward on the other. After discussing the implications of these results for various learning theories, the authors conclude by suggesting “that elicitation of the consummatory response appears to be a more critical primary reinforcing factor in instrumental learning than the drive reduction subsequently achieved.”

“Drive reduction” corresponds to negative reinforcement effects, the satiation of hunger in this case. They removed these effects by using a substance that had no nutritional value. The study showed that while the rats gained no calories, eating a tasty but nutritionally empty substance could be an effective reinforcer.

In 1952 Miller and Kessen published “Reward effects of food via stomach fistula compared with those of food via mouth.” Here is the abstract:

Rats prepared with stomach fistulas were trained in a simple T-maze under hunger motivation and with rewards of milk for correct choices and isotonic saline for incorrect choices. Different groups received milk in a dish or milk injected directly into the stomach. While both groups reduced errors and time significantly, the “milk-by-mouth” group learned more rapidly. “These results show that milk injected directly into the stomach serves as a reward to produce learning, but that milk taken normally by mouth serves as a stronger reward to produce faster learning.”

This says that even for an animal that is food deprived (“under hunger motivation”) there is a reinforcement effect beyond satiation of hunger. What’s left? Positive reinforcement. It’s not controversial to say that eating food is pleasurable. What’s interesting is that this experiment shows that it is pleasurable aside from satiation.

If eating were exclusively about negative reinforcement, most of us would skip dessert

If eating were exclusively about satisfying hunger, most of us would skip dessert–photo credit Wikimedia Commons

Makes Sense to Me

Actually, we know this intuitively. We have taste buds. Preferred foods taste good to us. It’s a major pleasure. How many of us will eat something we really like even after we are full? Some of us could easily do that three times a day!

I don’t know if all animals have taste buds, but most organisms must have a method for discriminating for appropriate foods. Doesn’t it make sense that organisms would have a survival advantage if they got immediate feedback about this, rather than having to wait until they have digested the food?

And it doesn’t take much observation to conclude that dogs enjoy food, does it?

There has been a lot of research on this topic and I have yet to find an experiment that had an opposing result. The same effects have been shown with water consumption and even sexual activity  (Sheffield, Wullf, and Backer, 1951), both primary reinforcers. And a personal note: I don’t enjoy reading about these unfortunate experimental animals, whose lives were almost certainly short and painful. But since the knowledge has already been gained from the studies, the least we can do is pay attention to it.

Dark meat chicken chunks for agility training

The good stuff: dark meat chicken chunks for agility training

So back to food. Even if your dog is extremely hungry and you expect that negative reinforcement will be involved if you use food to train, the studies say that there is also positive reinforcement even in that extreme situation. Taste buds probably don’t turn off when animals are famished.

There’s another aspect that I haven’t seen mentioned in a study but a smart FaceBook friend mentioned. Putting a treat in your mouth and getting pleasure from tasting and swallowing the food are perfectly and immediately correlated. But there is not a one to one correlation between each piece of food and a perceptible reduction in hunger. At least in humans, satiation is delayed. If you have a perfect meal in front of you with the exact volume of food and number of calories to fill you up, and you divide it up into 30 bites, your hunger is not assuaged 1/30th with every bite. The relationship is just not going to be that salient. The diminishment of hunger is probably delayed, and less linear. The positive reinforcement component would almost have to be stronger, which is what the studies with rats found.

Maximizing Positive Reinforcement

If you are still worried about a negative reinforcement component with training with food, it’s easy to address.  To minimize (and possibly eliminate) the presence of negative reinforcement effects, how about this: don’t train your dog on an empty stomach. Meaning the dog’s stomach, silly! But it’d probably be good if you have eaten something too. You want to be at your best when training!

Use appropriate sized pieces of good treats and you can be fairly confident that you are training with virtually entirely positive reinforcement (if the behavior increases, of course). If calories are a concern, cut down the next meal. Also, recent research indicates that dogs, just like people, probably learn better when their stomachs are not empty.  Makes me feel good that I have almost always given my dogs some of their meal ahead of time to take the edge off before training.

I’ll be writing more about the movement to eliminate the terms “positive” and “negative” from the technical descriptions of the processes of operant learning, and the nature of reinforcement in general. It’s a pretty interesting topic. In the meantime, you folks who are training with food: you can sleep well at night.

Thanks for reading!

Coming up:


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About eileenanddogs

Passionate amateur dog trainer, writer, and learning theory geek. Eileen Anderson on Google+
This entry was posted in Behavior analysis, Dog training hints, Negative Reinforcement, Operant conditioning, Positive Reinforcement, Reinforcement and tagged , . Bookmark the permalink.

14 Responses to Can We Determine Whether Training with Food Is Positive or Negative Reinforcement?

  1. Donna Hill says:

    Great tips. I too advocate making sure dogs have food in their stomach before training, especially for small dogs. Low blood sugar in the brain lowers impulse control and the dog can’t focus as well. I know I don’t function well until after i have my breakfast!
    I also train AFTER my dogs have been fed for the night (the timing is usually better for me) and both dogs are just as willing to train as when they are partially fed in the morning.

    • Great point about impulse control! I often end up training kind of late at night and everybody seems quite game and happy for a training game and a before-bed snack (no puppies right now!). Thanks for the comment, Donna.

  2. Ingrid Bock says:

    Great post. Your posts always are. I have been struggling to get clear on the quadrants. Inspired by this post, I started writing them up for myself, and stuck another snag. Would it be OK if I ran it by you?

    • Sure, Ingrid! You can use the email link in the sidebar of the blog. If you don’t want to paste the whole thing in there, just send a short email. I’ll write you back. Don’t want to put my email address in here because of spammers.

  3. cellopets says:

    I always enjoy your posts, and this one is no exception. I’ve struggled with the quadrants. I can understand them, but only for moments at a time. Inspired by the clarity of what you wrote here, I began writing them up for myself in a way I thought might stick, but I encountered a snag. Would it be OK if I ran it by you?

    • Sure, cellopets! I’d be flattered. You can use the email link in the sidebar of the blog. If you don’t want to paste the whole thing in there, just send a contact email and I’ll send you my address back.

  4. The Pet Care Magician says:

    My personal dogs are trained on a full stomach and will happily leave food in their bowls to cone and play training ganes with me. In my client’s dogs in training I will ask them to cut back on a morning feed just a bit for the first couple of trainig sessions just until the dogs build up a reinforcement history for food. After that it makes no difference if they are fed or not. If I have a client concerned about calorie intake then I tell them to feed less next meal if they are worried.

  5. KB says:

    I just wrote a long comment and the software replied “Sorry, this comment cannot be posted”, and then promptly made it disappear. Negative training, I think 🙂

    Here’s the short version. I am an avid positive trainer. However, in working with my very sensitive (fearful) dog, I sometimes think that she views it as very “negative” when I do not give her a treat after a “wrong” response to a cue. Isn’t withholding food for wrong responses technically a negative part of “positive training”?

    • Hi KB,

      Sorry WordPress ate your post! That is frustrating.

      As I understand it, withholding food is neither punishment nor reinforcement (obviously not the latter!). If the food is in your pocket, it stays in your pocket. It’s not taken away or added to the situation. However, the process that can be going on for the dog is extinction. (Some people call that the “fifth quadrant.”)

      If your dog has been reinforced for something in the past, then guesses wrong when you give a cue and you don’t pay, the behavior can go extinct (in that context). This is actually what you want, since you want the correct response to the cue. But of course you’d rather it not happen in that frustrating way of course.

      Extinction can be very unpleasant. Think of when your car doesn’t start or the elevator doesn’t come when you press the button. The thing that you anticipate happening suddenly doesn’t work anymore.

      Obviously I don’t know anything about your situation except what you have mentioned, but if this is happening a lot with your dog, you may possibly be applying the cue too soon.

      I have two dogs who used to really hate missing a click. Gradually with some experience they have learned that the world won’t end. But I think you are astute to notice this “down side,” especially for sensitive dogs.

      Some people do say that withholding a click is a sort of negative punishment, since the dog is “expecting” the treat and doesn’t get it. But to strict behaviorists, expectation is not relevant. The dog never had the food to begin with, so it can’t be taken away.

      You asked, “Isn’t withholding food for wrong responses technically a negative part of “positive training”? Negative has a technical meaning in learning theory. So I would say no to your question, since withholding the C/T is technically neither negative punishment nor negative reinforcement. But negative in the sense of unpleasant, you bet! Extinction can be a real drag!

      That’s great that you pay close attention to your dog’s responses, since I know you want it to be as fun as possible.


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  8. Karen Pryor in her book “Lads Before the Wind” which is about her dolphin training days wrote about dolphins getting really upset / angry when they didn’t get a treat they thought they had earned. Sort of like a teenager having a tantrum because Mom took their phone away and has the flavor of -P, at least from the dolphins perspective.

  9. Graham Mann. says:

    An excellent thought provoking article Eileen. I shall certainly be explaining this to any “doubters” in the future.

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